1. Field of the Invention
This invention relates to a pushbutton switch, and more particularly to a pushbutton switch for use on keyboards of electronic typewriters, word processors, computer terminal units or the like, which produce a snap feeling and a click sound.
2. Related Art
In order that a pushbutton switch for electronic typewriters and other machines may be easy for the operator to manipulate with reduced fatigue, the switch preferably produces a click or snap feeling and a click sound when pressed. As an example of a known pushbutton switch adapted to give such a snap feeling and a click sound, there is the device disclosed in Japanese laid-open Utility Model Application No. 19928/1986.
Thus, as shown in FIGS. 7 and 8, this pushbutton switch comprises a housing 1, a pushbutton 2 accommodated in said housing 1 in such a manner that it can be vertically movable within and with respect to said housing 1, a switch element 3 which is disposed within said housing 1 and which responds to the vertical movement of said pushbutton 2, and a plate spring 4 which is disposed in said housing 1 and adapted to produce a feeling and a click sound in response to the vertical movement of said pushbutton 2.
As the pushbutton 2 is depressed, it presses an arm portion 4a extending from the top of said plate spring 4, whereupon a bend portion 4b of said plate spring 4 is displaced away from an inner lateral wall 1a of said housing 1 toward the pushbutton 2 until the bend portion 4b hits a projection 1b of housing 1 to produce a click sound. In the course, a pressure plate spring 5 is also pressed but does not yet actuate the switch element 3. As the pushbutton 2 is further depressed, it rides on a tip portion 4c of the arm 4a of said plate spring 4 to thereby produce a click or snap feeling. Furthermore, the pushbutton 2 presses the tip portion 4c of plate spring 4 in a transverse direction to let the plate spring 4 return to the inner lateral side 1a of housing 1, whereupon a click sound is produced. At the same time, the pushbutton 2 actuates the switch element 3 through the pressure spring 5. The pushbutton 2 is biased by a coil spring 6 in a release direction (toward the upper position).
In this switch construction, as the pushbutton 2 is depressed, the plate spring 4 is flexed to cause its bend portion 4b to hit the lateral wall 1a of the housing 1 and the projection 1b to thereby produce click sounds. However, since the amount of flexure of the plate spring 4 is fixed, the loudness of the click sound cannot be varied, even though it is desirable to vary the loudness of kinds of switches.